Gender Disparity in Bladder Cancer and Chemopreventive Intervention

描述(申请人提供)：膀胱癌(BC)是男性第四常见的癌症，但BC的发病率在不同种族的男性中几乎是女性的4倍；根本原因尚不清楚。缺乏这方面的知识阻碍了预防该病的进展。根据我们已发表和未发表的数据，我们假设肝脏UDP-葡萄糖醛酸基转移酶1A3(UGT1A3)是人类BC发育中性别差异的关键决定因素，它通过将雄激素信号转化为增加尿中芳胺类致癌物向膀胱组织的输送。芳香胺，特别是4-氨基联苯(ABP)，是人类BC的主要原因。我们还假设萝卜硫素(SF)，一种常见的饮食植物化学物质，可以通过增强膀胱中的细胞保护防御来阻止UGT1A3促进芳胺诱导的膀胱癌的发生。这些假说将通过培养细胞和转基因小鼠模型的互补方法在四个特定目标上进行检验。目的1是验证我们的假设，即肝脏UGT1A3是决定BC发育中性别差异的关键分子。野生型小鼠和UGT1A3转基因小鼠(肝脏特异性和雄激素非依赖性表达)将在ABP诱导的膀胱癌发生方面进行比较。还将对去势和不去势的小鼠进行比较。另一种致癌物质2-乙酰氨基荧烯(2-AAF)将被用来排除ABP的特异性作用。目的2研究UGT1A3基因多态性对ABP和2-AAF催化活性的影响，以及对ABP和2-AAF诱导的膀胱细胞和肝细胞DNA损伤敏感性的影响。UGT1A3基因存在6个单核苷酸多态。所有的多态变异以及野生型基因都将被评估。目的3验证我们的假设，即SF可以通过刺激膀胱对芳胺类致癌物(ABP和2-AAF)的细胞保护性防御来阻断UGT1A3促进膀胱癌的发生，而不调节肝脏中的UGT1A3。不干扰肝脏UGT1A3可能是可取的，因为这种酶可能在生理上很重要，例如代谢雌酮。SF是一种很有前途的防癌药物，通过尿液排泄选择性地给药到膀胱组织。两种动物模型将被用来检验这一假设，包括上述UGT1A3小鼠模型和TG-UGT1小鼠模型(小鼠同时携带人类UGT1A3基因的编码和调控序列)。目的4在体内证实雄激素对UGT1A3的转录刺激作用，并阐明雄激素刺激UGT1A3的分子机制。这将通过使用细胞模型和TG-UGT1小鼠模型来实现。影响：拟议的研究有望导致阐明不列颠哥伦比亚省性别差异的分子基础，并制定有效预防这种疾病的新战略。

DESCRIPTION (provided by applicant): Bladder cancer (BC) is the 4th most common cancer in men, but BC incidence is nearly 4 fold higher in men than in women across race; the underlying cause is not understood. Lack of such knowledge impedes progress in BC prevention. On the basis of our published and unpublished data, we hypothesize that hepatic UDP-glucuronosyltransferase 1A3 (UGT1A3) is a key determinant of the gender disparity in human BC development through converting androgen signal to increased urinary delivery of arylamine carcinogens to bladder tissue. Arylamines, 4-aminobiphenyl (ABP) in particular, are the main cause of human BC. We also hypothesize that sulforaphane (SF), a common dietary phytochemical, can block UGT1A3 from promoting arylamine-induced bladder carcinogenesis by boosting cytoprotective defense in the bladder. These hypotheses will be examined in four specific aims using complementary approaches of cultured cells and transgenic mouse models. Aim 1 is to test our hypothesis that liver UGT1A3 is a key molecule that determines the gender disparity in BC development. Wild-type mice and UGT1A3 transgenic mice (liver- specific and androgen-independent expression) will be compared for ABP-induced bladder carcinogenesis. Comparison will also be made between mice with and without castration. Another carcinogen 2- acetylaminofluorene (2-AAF) will be used to rule out ABP-specific effects. Aim 2 is to assess the impact of UGT1A3 polymorphism on its catalytic activity toward ABP and 2-AAF and on the susceptibility of bladder cells and liver cells to DNA damage induced by ABP and 2-AAF. Six single nucleotide polymorphisms occur in UGT1A3 gene. All the polymorphic variants together with the wild-type gene will be evaluated. Aim 3 is to test our hypothesis that SF can block UGT1A3 from promoting bladder carcinogenesis by stimulating cytoprotective defense against arylamine carcinogens (ABP and 2-AAF) in the bladder, without modulating UGT1A3 in the liver. Non-interference of liver UGT1A3 may be desirable, since this enzyme may be physiologically important, such as metabolizing estrone. SF is a promising cancer-preventive agent and is selectively delivered to bladder tissue through urinary excretion. Two animal models will be used to test the hypothesis, including the UGT1A3 mouse model described above and the Tg-UGT1 mouse model (mice carry both the coding and the regulatory sequences of the human UGT1A3 gene). Aim 4 is to confirm that UGT1A3 is transcriptionally stimulated by androgen in vivo and to elucidate the molecular mechanism by which androgen stimulates UGT1A3. This will be accomplished by using both cell models and the Tg-UGT1 mouse model. Impact: The proposed studies are expected to lead to the elucidation of the molecular basis of the gender disparity in BC and the development of new strategy for effective prevention of this disease.